The present invention relates to thin-walled plates provided with reamed holes via which such plates can be threaded onto centering means, particularly for forming packets of such plates into an ink printing head in sandwich structure, for which purpose the plates are provided with recesses in the form of perforations or semiperforations.
These plates are made of thin-walled sheet metal, metal foil or foils of a ferrous or nonferrous material, and particularly are plates into which structures, cavities, channels or other shapes have been etched. The plates, when assembled in a packet, are bonded together, for example by a diffusion welding process, and then form fluidic elements used, for example, in the control and regulating art to conduct and deflect flowing media.
Such arrangements are also utilized in ink printers where they constitute ink printing heads having a sandwich structure. The latter present chambers and channels which have been combined into pressure systems as well as inlet and outlet channels for the printing fluid to be applied to a print carrier. For structural design reasons, the energy flow channels of the pressure systems, the ink inlets and outlets for the nozzles change their position and direction within the plates. Often the nozzles are shaped by means of semi-etching into oppositely disposed plates. The slightest inaccuracies and tolerances during manufacture, assembly and during the subsequent heat treatment process lead to offset junctions, overlaps in the channel and nozzle paths etc., which interfere with the passage of the fluid and counteract the controlling effect and the discharge of the fluid.
An ink printing head of this type is disclosed, for example, in German Offenlegungsschrift [Laid-open Application] No. 2,649,970. The cavities and channels passing through the individual plates at different levels exhibit, for example, smaller cross sections in the regions of higher flow speeds, in order to produce such higher flow speeds, so that an inaccuracy in the transition of one channel from plate to plate would have the effect of an even greater interference in the flow behavior and a reduction in the actual discharge speed from the nozzle. Since the plates of such an ink printing head are constituted by foils of a few hundredths of a millimeter in thickness, reamed holes can not be worked and fitted to have a normal press fit on the centering means if extensive deformation of the plate is to be avoided when it is placed onto the centering means.
Although German Auslegeschrift [Published patent Application] No. 2,359,110 discloses a displaceable bar which can be elastically deformed in a radially outward direction for the purpose of clamping a shaft in a bore, extreme accuracy is not a requirement in seating such a shaft and deflection in all directions as a result of pressing the shaft into the bore does not take place so that this arrangement does not serve to maintain centering distances.